Gnome Screen Resolution doesn't match X11/xorg.conf - how do I edit my resolutions?!
 

Distro: Debian Etch.
Select parts of /etc/X11/xorg.conf (I don't think I removed anything pertinent)
Gnome's "Screen Resolution Preferences" app offers me 1280x1024 and 1024x768.

gconf-editor: /desktop/gnome/screen/debian/0 has resolution="1280x960"

Why don't they match up? How do I get 1600x1200?

Just a thought, but what happens if you remove the other resolutions and only leave the "1600x1200" ?

Make sure you have a backup first.
Run in bash to restore it if it doesn't work.

With some drivers /var/log/Xorg.0.log gives a fairly clear description of why certain display modes were rejected. It's worth checking.

That maximum horizontal rate of 68 is rather low for a resolution with 1200 scan lines. It isn't impossibly low, but it is low enough that if you convinced the system to do 1600x1200 at 68 or lower HorizSync you wouldn't like the results.

If your monitor can do a decent job displaying 1600x1200 it's correct maximum HorizSync is probably higher than 68.

I think that tells the driver to ask the monitor for various information, such as HorizSync. But if you also tell it the HorizSync, I'm not sure which wins. I think I solved some similar problems by temporarily removing the HorizSync line, forcing it to really use DPMS. But once that fixed the problem, I didn't want to leave it that way (because it requires the monitor to be on everytime X starts) so I found the correct HorizSync in /var/log/Xorg.0.log when using DPMS and edited it back into xorg.conf

Gnome's "Screen Resolution Preferences" app now offers:
1280x1024, 1024x768, 800x600, 640*480
Where do those come from?

/var/log/Xorg.0.log
DPMS is enabled later on.

Well, there is the culprit. The video driver says, 'Not using mode "1600x1200" (no mode of this name)' and procedes to pick its own built-in modes. Except it has 1600x1200 modes. I'll try setting the /etc/X11/xorg.conf mode to "3a", "4b" etc and see if it works...

What is needed to restart X11? If it sufficient to make a new login? Or do I need to restart GDM? Or reboot the entire system?

What's it want from me?

If we really believe that message (as opposed to some other misconfiguration makes it think there is no mode of that name) then you need to provide a modeline in the xorg.conf file. There are lots of other threads discussing how to do that, but I don't have URLs handy. (Adding a modeline in xorg.conf is the most effective and flexible solution even if the message is wrong and some simpler method would work).

There are a few utility programs for constructing modelines. The one whose name I remember is xvidtune. I could never get the TEST button in xvidtune to work and for my intended purpose it was useless without the TEST button. But xvidtune can write modelines out to the terminal session from which it was launched (it is a GUI program, but seems to be intended to be launched from a terminal session in GUI mode, unless I misunderstood something).
One of the other modeline generating programs might be more appropriate, but I forget the names.

However, I think you should fix that maximum horizontal sync value first, or it will interfere with anything else you try.

Regardless of whether you force a modeline in xorg.conf or it finds a modeline, that modeline is still constrained by that low maximum sync.

xvidtuner says (when I hit test) "Sorry: You have requested a mode-line\nThat is not possible, or not supported by your hardware configuration"

Where in the xorg.conf file do I stick a modeline?

In the "Monitor" section of xorg.conf. On my system, "man xorg.conf" is actually pretty thorough. I like Etch but have never found setting up / getting all of the man pages together to be easy; here's the skinny on ModeLine, shamelessly copied from 'man xorg.conf':

"ModeLine "name" mode-description
This entry is a more compact version of the Mode entry, and it also
can be used to specify video modes for the monitor. is a single
line format for specifying video modes. In most cases this isn’t
necessary because the built-in set of VESA standard modes will be
sufficient.

The mode-description is in four sections, the first three of which
are mandatory. The first is the dot (pixel) clock. This is a sin-
gle number specifying the pixel clock rate for the mode in MHz.
The second section is a list of four numbers specifying the hori-
zontal timings. These numbers are the hdisp, hsyncstart, hsyncend,
and htotal values. The third section is a list of four numbers
specifying the vertical timings. These numbers are the vdisp,
vsyncstart, vsyncend, and vtotal values. The final section is a
list of flags specifying other characteristics of the mode. Inter-
lace indicates that the mode is interlaced. DoubleScan indicates a
mode where each scanline is doubled. +HSync and -HSync can be used
to select the polarity of the HSync signal. +VSync and -VSync can
be used to select the polarity of the VSync signal. Composite can
be used to specify composite sync on hardware where this is sup-
ported. Additionally, on some hardware, +CSync and -CSync may be
used to select the composite sync polarity. The HSkew and VScan
options mentioned above in the Modes entry description can also be
used here."

Good luck with it; sounds like it's put you through the mill...

- Larry

Hey,

I am just puzzling the same thing. I have to use
and find they are in /etc/gnome-settings-daemon/xrandr/monitors.xml.
I am using 2.30.2. I do not know if this applies to your GNOME version.;)

Update:

I was not correct. The modes GNOME gives to your actually comes from xrandr. It seems GNOME gets them on the fly not from any configuration files. You may use xrandr to display available modes which are exactly the same with what GNOME gives us:

tux@dell:~$ xrandr
Screen 0: minimum 320 x 200, current 2390 x 768, maximum 8192 x 8192
VGA1 connected 1024x768+1366+0 (normal left inverted right x axis y axis) 306mm x 230mm
1280x1024 60.0
1280x960 60.0
1152x864 75.0
1024x768 85.0* 75.1 70.1 60.0
832x624 74.6
800x600 100.0 85.1 72.2 75.0 60.3
640x480 100.0 85.0 72.8 75.0 60.0
720x400 70.1
640x350 70.1
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
1366x768 60.0*+
1360x768 59.8 60.0
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
DP1 disconnected (normal left inverted right x axis y axis)

Yes. But is is really cryptic to find where GNOME get the available resolutions. I was having the same problem as yitzle and Google lead me here. Hope my reply will be of help to future googlers. :)